ColdFusion - Create multidimensional array dynamically

Question

I'm using CF 10. As a script is running, I am creating an array containing distinct values that represent a single vehicle. I'm initializing the array at the top of my script using

<cfset myArray = ArrayNew(1)>

Then as I am running my script I'm appending to it using...

<cfset temp = ArrayAppend(myArray, myQuery.VIN)>

This all works fine, but what I want to do is after each section in the script is reached, I want to update any VINS in my current section query so that they are an array of values. So the Array that was..

[1]["VIN NUMBER 123"] [2]["VIN NUMBER 456"]

becomes...

[1]["VIN NUMBER 123"]["VALUE1"] ["VALUE2"] ["VALUE3"] [2]["VIN NUMBER 456"]["VALUE2"]

I thought I could do something like this...

<cfset vindex = ArrayFind(myArray,vinToFind)>
<cfif NOT IsArray('myArray[vindex]')>
     <cfset myArray[vindex] = ArrayNew(1)>
</cfif>
<cfset temp = ArrayAppend(myArray[vindex],valueToAppend)>

but in the end, my array is still one dimensional. What am I doing wrong?

Rather than a multidimensional array, you probably want an array of structs. (Or, possibly, an array of arrays.) — ale
– ale, Commented Dec 30, 2016 at 18:45
Does this script involve looping through query results? If so, the group attribute of cfoutput might be useful. — Dan Bracuk
– Dan Bracuk, Commented Dec 30, 2016 at 18:45
@DanBracuk - it does, but it involves looping over a query result and then performing specific tasks on that result, which is where I want to create array within array if necessary. I think I'll just use array of arrays. — Phil
– Phil, Commented Dec 30, 2016 at 19:43
@ale That is exactly what I'm trying to do, but I'm not sure why my code above is not allowing me to create array within the array index specified. — Phil
– Phil, Commented Dec 30, 2016 at 19:44
Out of curiosity, why do need to use arrays? Usually arrays are better when order is important. However, if you need to access something by key, as you do here, structures are better. — Leigh
– Leigh, Commented Dec 31, 2016 at 2:04

Alex · Accepted Answer · 2016-12-30 21:20:04Z

I recommend an array of arrays as suggested by @ale.

<cfset myArray = ArrayNew(1)>

<!--- check if the VIN is already present --->
<cfset vindex = ArrayFind(myArray, vinToFind)>

<!--- the VIN was found --->
<cfif (vindex gt 0)>

    <!--- if the VIN is still on its own, transform it to an array --->
    <cfif NOT IsArray(myArray[vindex])>
        <cfset temp = myArray[vindex]> <!--- remember current VIN --->
        <cfset myArray[vindex] = ArrayNew(1)> <!--- transform present index to an array --->
        <cfset ArrayAppend(myArray[vindex], temp)> <!--- add VIN back in --->
    </cfif>

    <!--- add the VIN --->
    <cfset ArrayAppend(myArray[vindex], valueToAppend)>

<!--- VIN is not present yet --->
<cfelse>
    <cfset ArrayAppend(myArray, valueToAppend)>
</cfif>

Here are some tips:

ArrayAppend(1) can be written as [].
ArrayAppend(myArray, value) can be written as myArray.add(value).
There's usually no need to store the return of ArrayAppend as it will always return true. Just go with <cfset ArrayAppend(myArray, value)>.
IsArray expects a variable, not a string. IsArray("myArray") will always return false while IsArray(myArray) would return true.

The above code using array literals and the add method.

<cfset myArray = []>

<!--- check if the VIN is already present --->
<cfset vindex = arrayFind(myArray, vinToFind)>

<!--- the VIN was found --->
<cfif (vindex gt 0)>

    <!--- if the VIN is still on its own, transform it to an array --->
    <cfif not isArray(myArray[vindex])>
        <cfset myArray[vindex] = [ myArray[vindex] ]> <!--- transform present index to an array --->
    </cfif>

    <!--- add the VIN --->
    <cfset myArray[vindex].add(valueToAppend)>

<!--- VIN is not present yet --->
<cfelse>
    <cfset myArray.add(valueToAppend)>
</cfif>

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